A new Democratic National Committee (DNC) rule will make sure candidates for president are only affiliated with the party, enraging Bernie Sanders supporters.

Fox News reports that the DNC voted June 8 to force presidential candidates in 2020 to declare themselves as Democrats before announcing their candidacies.

U.S. Sen. Bernie Sanders, who affiliates as an independent, ran against Democrat Hillary Clinton in the 2016 race and gave the former secretary of state and New York senator a serious challenge for the party’s nomination.

The at-times bitter primary pitted the progressive wing of the Democratic Party against its more moderate and centrist side.

Sanders supporters were quick to react to the news, saying that the party was being vindictive and seeking a form of revenge for the 2016 election cycle, according to the report.

“We just came off a devastating presidential loss in 2016. It would seem to me the actual impetus would be to expand the Democratic party. I just for the life of me don’t see any motivation for this beyond personal spite,” 2016 Sanders Senior Advisor Mark Longabaugh said in the article.

According to the article, despite calling himself an independent, Sanders has also labeled himself as a “Democratic Socialist” and regularly caucuses with the Democrats.

The Vermont senator filled rallies and campaign events, many on college campuses, with a message of providing universal healthcare and free college tuition while railing against wealthy Americans and condemning income inequality.

Clinton eventually won the nomination, but questions were raised about the influence she had on the DNC, which was supposed to remain neutral during the primary process.

Featured image credit: Cliff OwenAP Photo

Then DNC Chairwoman U.S. Rep. Debbie Wasserman Schultz came under fire and eventually resigned her position amid allegations of favoritism and collusion with the Clinton campaign.

Clinton went on to lose in the general presidential election to Republican real estate tycoon Donald Trump in a race that shocked pollsters and pundits alike.

The new DNC rule would bar candidates such as Sanders from running in 2020 unless he formally joins the Democratic Party before announcing his candidacy, according to the story.

The decision could also impact Sanders’ practice of running for the Democratic nomination in his senate bids despite formally being an independent, according to the article.

According to the story, Sanders would get, then refuse, that party’s nomination and run as an independent on the ballot instead.

By following this strategy, Sanders has been able to thwart potential Democratic challengers facing him in the general elections, according to Fox News.